1. Field of the Invention
The invention relates generally to a portable power tool, particularly to an adjustable base therefore.
2. Background Art
Conventional portable saws typically include a planar base upon which the tool is supported during the cutting operation to provide a consistent angle of cut relative to a top surface of an associated workpiece. Many conventional prior art portable saws are provided with an adjustable base for permitting a user to select an angle of the base relative to the cutting plane of the portable saw to thereby provide a user selected cutting angle relative to the surface of the workpiece. This angular adjustment of the cutting plane relative to the workpiece is commonly referred to as the bevel angle and is measured as the offset from orthogonal to the workpiece.
Some conventional prior art portable saws with adjustable bases include a fastener, such as a threaded screw or bolt that must be loosened so that the base may be adjusted and tightened to secure the orientation of the base. However, the use of a fastener may require utilization of a separate tool which may be inconvenient to a user. Alternatively, prior art adjustable bases may include a threaded fastener with a knob formed thereon, yet compactness may limit the size of the knob thus limiting the torque that may be applied by the user which may result in a non-secure attachment of the base to the power tool.
Accordingly, the prior art has provided selective adjustment of the base to the portable saw by use of a threaded fastener that is tightened and loosened by utilization of an elongate lever extending from the fastener or a nut that is threadably engaged to the fastener. Due to the length of the lever, limited rotary displacement of the lever may be permitted because of compactness of the tool or size restraints. Accordingly, such prior art adjustable bases that utilize a threaded member typically permit less than a half turn of the lever thus limiting the range of torque provided to secure the base to the tool and/or limiting the amount of clearance provided to adjust the base relative to the tool.
Accordingly, the prior art teaches adjustable bases that utilize a toolless clamping mechanism with a lever mounted to a double threaded fastener with the threads in opposed directions, to provide twice the displacement per angular rotation in the limited range of manual rotation. The prior art also provides a threaded engagement that has an unlimited range of manual rotation, yet requiring additional effort by the user. Other prior art toolless adjustable bases have avoided the attachment by a threaded member altogether by utilizing an offset lobe clamp member. Some offset lobe clamp member designs may be inconvenient to the user, by requiring removal of a baseplate from the adjustable base before the lever can be fully rotated to the unlock position.
A goal of the present invention is to provide a toolless adjustable base for a portable saw that is convenient to a user by providing both sufficient clearance to adjust the base and sufficient torque to reattach the base relative to the tool while minimizing the effort and the range of motion required by the user.